The present invention relates to a sealing system using a metal gasket with a bead projecting outwardly from the gasket for sealing between two engine parts.
In a metal gasket, it is common to form a bead on a metal plate around a hole to be sealed. When the gasket with the bead is tightened between the two engine parts, the bead is compressed by the engine parts, so that the bead is flattened and generally forms a plurality of corrugated beads to tightly seal around the hole to be sealed.
In a steel laminate gasket formed of a plurality of metal plates, although a bead may be formed on an outer plate to extend outwardly from the gasket, since the strong sealing pressure is generally formed on the compressed or corrugated beads, if the corrugated beads directly abut against an engine part, the engine part may be deformed or partly dented by the corrugated beads. Also, a sealing portion, i.e. top portions of the corrugated beads abutting against the engine part, is narrow.
Therefore, in case the bead is formed on the outer plate of the steel laminate gasket, the bead is formed to orient toward another plate of the gasket. Namely, the bead does not directly abut against the engine part.
In case the bead is formed on a middle plate between the two outer plates, when the bead is compressed, the bead is flattened and pushes the outer plate against the engine part. As a result, a relatively large sealing portion is formed by the bead, which orients toward the engine part.
As explained above, in case the bead is formed on the middle plate, relatively large sealing pressure is formed between the gasket and the engine parts. Therefore, the bead is generally formed in the middle plate around a hole to be sealed.
In a diesel engine, very high pressure is formed inside a cylinder bore when actuated, such as 120-140 kg/cm.sup.2. Lately, the combustion pressure is going to increase further. Consequently, although a cylinder head is tightly attached to a cylinder block by bolts, the cylinder head moves or vibrates in the directions toward and away from the cylinder block.
In case the pressure of 120 kg/cm.sup.2 is formed inside the cylinder bore, the cylinder head moves about 4 micro meters in a vertical direction. In case the pressure of 140 kg/cm.sup.2 is formed, the cylinder head moves about 5 micro meters.
In the diesel engine, although a steel laminate gasket with beads is installed between the cylinder head and the cylinder block, the gasket may not absorb such movement of the cylinder head. Especially, as the sealing ability decreases in a long usage, leakage may occur between the cylinder head and the cylinder block.
Namely, in a conventional gasket, a bead formed on a plate of a gasket is substantially completely flattened when compressed, so that elasticity of the bead is not sufficiently utilized. Therefore, it is difficult to completely seal between the engine parts which vibrate severely.
Accordingly, one object of the present invention is to provide a sealing system with a metal gasket, which can seal tightly even when high pressure is formed between two engine parts.
Another object of the present invention is to provide a sealing system as stated above, which can seal securely even when an engine part is slightly moved.
A further object of the present invention is to provide a sealing system as stated above, which is made simply and can be manufactured economically.
A still further object of the present invention is to provide the metal gasket, which can securely seal between the two engine parts.
Further objects and advantages of the invention will be apparent from the following description of the invention.